Adjustable pitch propeller



Feb. 25, 1936.

TNESSES F. W. CALDWELL ADJUSTABLE) PITCH PROPELLER Filed April 21, 1931 7 Sheets-Sheet 1 m. IL IL L Q as MA xIMuM INCREASE P1 TCH NgRMAL LADE P/Tcl/ B NA xm UM DECREASE Pl Tc H A INVENTOR Feb. 25,1936; LL 2,032,254

ADJUSTABLE PITCH PROPELLER Filed April 21, 1931 7 Sheets-Sheet 2 wrm g I INVENTOR E55 3 H $1 MW F. w. CALDWELL I ADJUSTABLE PITCH PROPELLER Filed April 21, 1931 '7 Sheets-Sheet 3' N R a m N n m w M @N 7 E L F- w QB 56TH F I UM G I II. +lrlriul :2: :2: .fiw wa kfi a Feb; 25, 1936.

F. w. CALDWELL 2 2,032,254

ADJUSTABLE PITCH PROPELLER Filed April 21, 1931 7 Sheets-Sheet 5 Q Q, 9 "s $3 2 i 1 Q I N "a a 1 N mum Feb. 25, 1936. F. w. CALDWELL ADJUSTABLE PITCH PROPELLER Filed April 21, 1951 7 Sheets-Sheet 6 WITN5SSE5 INVENTOR M-Jz.

Feb. 25;1936. F. w. CALDWELL 2,032,254

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ADJUSTABLE PITCH PROPELLER Filed April 21, 1931. 7 Sheets-Sheet 7 4 2 6 a A B C ANGULAR Pas/770M 0F BLADES WITNESSES INVENTOR /iwmW Patented Fa. 25, 1936 UNITED STATES PATENT OFFICE ADJUSTABLE PITCH PROPELLER Application April 21, 1931, Serial No. 531,685 27 Claims. (01. 170-163) While controllable pitch propellers for aircraft have been proposed before, and some experiments have been made with devices intended to control pitch adjustment, most propellers have been constructed in such manner that the pitch angles of the blades can only be adjusted by mechanics on the ground. When the pitch angle of a propeller cannot be modified while the aircraftis in flight, the pitch angle at which the propeller is set is necessarily selected as a compromise between the angles most eflicient for flight under'various conditions.- For example, it is desirable that a propeller should be adjusted to low pitch during the take-off period. During it the airplane necessarily moves at relatively low speed through the air, with heavy load on the propeller, and consequently, if the pitch of the propeller is too high, the resistance ofiered by the air to rotation of the propeller will be such as to hold the engine to a comparatively low speed. Engines do not develop maximum power at low speeds, and therefore, with a high-pitched propeller, the engine is most ineficient in the period when greatest power 7 is needed. 1

If on the other hand, the propeller is adjusted to a low-pitch position during the take-off period, offering minimum resistance to rotation, the en- I gine will be able to drive the propeller at normal engine speed, or somewhat above normal speed,

and a quick short take-01f and rapid elevation are possible. I

After the take-off has been completed, and the plane assumes its normal level flight, the speed of the plane through the air is considerably increased, the resistance to propeller rotation is decreased, and'tlie engine will-speed up. To avoid over-speeding, it is then necessary to throttle the engine down to normal speed. The engine will then be producing only a portion of the powerof which it is capable. Y

During level flight, it is desirable that the propeller be adjusted to high-pitch position so that it will absorb all of the available power of the engine, ofiering suflicient resistance to hold the engine to its-normal full-power speed with eflicient operation of the'propeller.

It is therefore an object of my invention to 'provide a propeller for aircraft having blades the pitch of which may be controlled during flight of the aircraft. Another object is to provide a propeller which may be adjusted by manuallycontrolled means to low-pitch position during the take-off period of flight, and readily changed by automatic constantly-operative centrifugallyactuated means to high-pitch position after the aircraft has attained normal level flight. Another object is to provide a controllable pitch propeller which may be moved and held in lowpitch position by fluid pressure means, and later allowed to move to high-pitch positionby the action of centrifugal force on a counterweight mechanism, upon release of the fluid pressure. A further object is to provide a controllable pitch propeller that will continue to operate as a fixed pitch propeller in the event of any accident to the adjusting mechanism.

An object of the invention is to provide automatic control mechanism for a controllable pitch propeller whereby the pitch may be regulated in response to changes in the engine speed, to maintain the speed of the engine substantially constant. A further object is to provide a controllable pitch propeller having adjustable limit stops to define a low-pitch position and a high-pitch position.

A further object is to provide improved methods of making and assembling controllable pitch propeller mechanisms.

In accordance with this invention I provide a propeller having blades journalled to turn about their longitudinal axes for pitch-changing, but fitted tightly to the hub to reduce to a minimum relativemotion therebetween during normal operatlon. blades, and adjustable limit stops define the lowpitch and the high-pitch positions. Fluid pressure means, suitably connected to the linkage, move the blades to low-pitchposition, as during the take-off period, and counterwelghts are provided forconstantly urging the linkage, by centrifugal force to move the blades to high-pitch position, the-counterweights being effective when pressure is released from the fluid pressured operated means. Governing means are provided, v operatively connected to the fluid pressure system,

by which it is possible to automatically adjust the pitch of the propeller during flight in response to variations in the speed of the engine, to maintain the engine speed substantially constant at -a speed to give most effective propeller operation.

Linkage is provided for moving the diagrammatically, a fluid pressure control system for operating it; Fig. 2 is an enlarged view, in longitudinal section, of the propeller shown in Fig. 1, taken on a plane at right angles to the plane of section thereof and represented the line IIII; Fig. 3 is a view similar to Fig. 2,

showing the propeller in elevation with the blades broken away and a modified fluid pressure control mechanism partly in longitudinal section and partly diagrammatically; Fig. -'l is a view in longitudinal section, similar to Fig. 2, of a modified propeller blade shanl: and thrust bearing therefor; Fig. 5 is a diagrammatic representation of a blank for a holloti stee propeller blade showing a method of applying a thrust bearing to it; Fig. 6 is a' representation of a completed hollow steel propeller blade with the thrust bearing in operation position; Fig. 7 is a view in longitudinal section of the governing device shown in Fig. 3 for controlling the fluid pressure system; Figs. 8, 9 and 10 are views in cross section of the governor, taken on the planes represented by the lines VIII'-VIII, IX-IX and X-X, respectively, in Fig. 7; and Fig. 11 is a graphical representation of the various twisting moments that act upon the propeller blades.

Referring more particularly to Figs. 1, 2 and 3 of the drawings, a controllable pitch prepeller embodying my invention. comprises, in general, a hub structure I upon which is mounted a plurality of propeller blades .2, extending from the hub; I in the plane of rotation and with their axes in alignment. The hub I is carried, in the usual manner, on the end of a hollow engine shaft 3, protruding from a crank case 4. The end of the shaft 3 is tapered to fit a complementary tapered bore in the hub I, and the exterior of the shaft is splined to mate with a similarlysplined interior surface of the hub. The hub i is held on the shaft 3 by a retaining nut {that engages threads on the end of the shaft and bears against the forward end of the hub.

The hub I is a one-piece structurecomprising in general a substantially cylindrical body portion from which extend'lntegrally formed arms 6 to constitute a spider having studs on which the blades 2 are mounted. The particular blades 2 shown in' the drawings are similar to conventional metallic blades insofar as their general shape and aerodynamic qualities are concerned.

The roots or shanks of the blades are hollow, and each blade root is bored, and fitted with an internal sleeve I i having internal bearing surfaces I2 and I3 that engage complementary journals on the arms 6. The bearing surfaces on the arms function to transmit driving torque to the blades and. permit them to be turned about their longitudinal axes for adjusting the pitch. .The sleeve II is provided with an inte gral laterally extending flange I4 that abuts against the end of the blade 2 and is provided with a laterally disposed bearing surface I5 that engages a complementary annular plane-bearing surface I6 on the body portion of the hub I encircling each stud 6 to cooperate with the stud in rigidly holding the blade 2.

The end of the blade adjacent the flange I4 is 'provided with an integral outwardly turned flange 2| to which the flange I4 is secured by dowels or screws 22. For holding the blades 2 0n the studs 6 with the flanges I4 tightly against the bearing surfaces I 6, each blade is provided with an anti-friction thrust bearing 23 disposed to encircle the blade shank and to bear against the outwardly turned flange '2I. The bearings 23 on the two blades are inter-connected by a r thrust resisting structure or barrel 24, having, at its ends, inwardly turned flanges 25 that engage the outer races of the thrust bearings.

As shown, the barrel 24 is split along its longitudinal axis in such manner that it may be fitted over the blade roots and the semi-cylindrical halves secured together by suitable bolts 26.- Openings are provided substantially the mid-- dle of each barrel half to permit it to fit over the cylindrical body portion of the hub I. The barrel 24 is made to fit the bearings 23 closely so that the blades 2 are held rigidly in position but may be turned about their longitudinal axes upon application of relatively large twisting force.

The blade may be made as shown in Fig. 4,

with a flange structure Zia made separate from the blade, applied to the blade by means of a screw threaded joint, and locked in position by The bearing 23, in this 2| is then formed by an upsetting process in the usual manner. The bearing 23 may be moved a considerable distance from the end of the shank,

permitting the upsetting of the shank end without damage to the bearing.. The flange 2| and the exterior of the shank are then machined to provide accurate seating surfaces after which the bearing 23 is moved down the shank to engage the seating surfaees. In case the blades used are of a light alloy requiring heat treatment after the upsetting operation to develop the full strength of the material, it is desirable to utilize bearings made of special steel of such character istics that its hardness is not aiIected by the tem perature used in heat treating the metal of flu blade.

In the event that blades of the hollow steel type shown in Figs. 5 and 6 are used, the bearing 23 may be applied to the heated blade after the flange 2I has been formed, but just before the blade has been pressed to its final shape. After the machining operations on the blade have been performed, the blank may be heated to a temperature suitable for pressing it to final shape.

and, while it is thus heated, the bearing 23 may,-

be slipped over the tip end, of the blank, as shown in Fig. 5', and moved to its normal position adjacent to the flange 2|. The blank is then placed in a press and flattened in to the desired propeller shape, with the bearing 23 retained permanently in position as shown in Fig. 6.

After the bearing 23 has been applied to the blade shank, the bushing II, which is preferably as for instance by dipping the shank in hot oil,

after which'the sleeve II is pressed into the hollow root or the blade to bring its flange I4 into contact with the flange 2! of its blade root. After the blade cools, it shrinks into very firm engagement with the sleeve II. However, in so shrinking, the shank causes the sleeve II to contract, and some distortion may result. To correct this, the bearing surfaces l2 and 3 on the interior of the sleeve II are accurately lapped to their final dimensions.

These surfaces, as well as their complementary surfaces on the spider or stud 6, may be hardened the annular bearing surfaces l6. The action of that condition.

.centrifugal force will feed the lubricant outwardly to lubricate the bearing surfaces l2 and I3.

As shown, the inner end of the sleeve II is reduced to what is known as a feather edge to permit it to flex with the blade during flight and 'thus avoid concentration of stress in the blade at the end of the sleeve. It is highly important in propeller construction to avoid all localization of stress. Fatigue cracks usually start from By fitting the blades 2 in this manner very accurately and tightly on the studs 6 of the hub I,

wear between the blades and the hub is reduced to a minimum. During flight there is constant vibration in the propeller structure, particularly in the blades, and if looseness occurs between the blades and the hub, relative motion will result in destructive abrasion.

Although the blades 2 are fltted closely to the hub i, it is possible by means of suitable apparatus that constitutes part of my invention, to

. turn the blades 2 for-adjusting the pitch .angle thereof, by means of an operating lug 3| formed integral with'the flange M of the sleeve and extending through a slot 32in thebarrel 24. The slot 32 is made of such length that the blade may be turned through a predetermined maximum angle .of adjustment, but'is prevented from turning to a position beyond the predetermined range. In a particular practical embodiment of my invention, a torque of substantially 2000 lb. inches is required to move the two blades 2 relative to the spider ti.

It is known that propeller blades in flight have a tendency to turn about theirlongitudinal axes to bringtheir major transverse axes into the plane of rotation of the propeller. This results from the twisting moments set up by the action of centrifugal force on the blades when the propeller is rotated. The tendency in flight is for the propeller to lose its pitch".

This inherent tendency of the blades to turn towards the zero pitch position has heretofore been utilized formoving the blades to low-pitch position, and suitable apparatus provided for moving the blades to high-pitch position. Since the speed at which an airplane engine operates, tends to vary inversely with the pitch of the .'blade, in practicing the present invention the to High-pitch position, thus *checking the speedof the engine. a

Inasmuch as the propeller is ordinarily set at high-pitch position during normallevel flight of the airplane, it is desirable to utilize mechanism can'ied by the propeller hub and constantly operative through centrifugal action to hold the propeller in the high-pitch position, rather'than to fluid pressure means for holding the propeller in high-pitch during normal flight.

To counteract the twisting moment resulting from the inherent effect of centrifugal force on the blades, and to provide operative twisting moment for moving the blades to high-pitch po-. sition, a pair of counterweights 4| is provided,

pivotally mounted at one end on a collar 42 surrounding the hub Each of the counterweights 4| is connected by a short link 43 to the operating lug 3| extending from the sleeve ll of the blade. The link 43 is pivotally connected to the lug 3| by such'means as a bolt 44, and is pivotally connected at its other end by a bolt 45 to the counterweight 4| at a point close to the center of rotation of the weight about its pivotal connection to the ring 42.

By reason of the short lever arm between the pivot axis of the counterweight and its connection to the link 43, a large mechanicaladvantage is obtained and the outer end of the counterweight moves through a relatively large angle in turning the blade from its low-pitch position to its high-pitch position. Consequently the counterweight 4| exerts a comparatively large force on the operating lug 3| of the propeller blade 2'.

Although the counterweight is very light in proportion to the remainder of the propeller structure, it being made of aluminum or similar -metal, the force exerted by it is suflicient to overcome the pitch-reducing moment of the blade resulting from centrifugal force and aerodynamic action, and to overcome the frictional resistance which results from thetight fitting manner in which the blade is mounted on the hubstructure. The range of motion through which the counterweight travels in accomplishing movement of the blade from low-pitch position to high-pitch position is shown diagrammatically in Fig. 1. From depend upon externally operated mechanical or this figure it may also be seen that the counterweights are shaped and pivoted in such manner as to cause their centers of gravity to move in an-arc so positioned that the torque exerted by the action of centrifugal force is substantially constant for'all pitch positions.

To overcome the action of the counterweights 4| to provide low-pitch position for starting, fluid pressure operating mechanism comprising a piston 5| is mounted on an extension of the propeller huh .I and concentric with the axis of rotation of the propeller. The piston 5| is connected to the counterweights 4| by links 52 pivoted at one end to lugs 53 on the piston 5|, and at their outer ends to the counterweights 4|, by means of bolts 54, at a position a considerable distance from the point at which the counter-- weights are pivoted on the collar 42. In this manner a relatively long lever arm is provided for the connecting rod 52 in turning the counterweight, and consequently the piston 5| is enabled to'move a considerable distance with a large mechanical advantage in turning the propeller from high-pitch to low-pitch position.

To actuate the piston, oil from the engine lubricating system is admitted through the hollow shaft 3. is utilized ordinarily only for brief periods, as for instance when the airplane is taking off, any leakage which may occurfrom the fluid actuated piston 5| is of little consequence.

. The high-pitch and low-pitch positions of the 4 Inasmuch as the low-pitch position propeller blades may be determined by adjustable stop members that cooperate with'lugs 55 on the surface of the piston As shown in Figs. 2 and 3, the lugs 55 are provided with openings through which pass threaded studs 56 screwed into the barrel 24 at their inner ends and supported at their outer ends by a spacing ring 57. Pairs of lock nuts 58 and 59 are provided at the inner and outer ends of the studs 55 respectively, for engaging the lugs 55 to prevent further movement of the piston 5| after the blades have been turned to the predetermined angular position at either end of the range of operation.

To set the'mechanism to provide predetermined high-pitch and low-pitch positions, the blades may be turned manually, by exerting force on the counter-weights 4|. For example, the blades may be first moved to a predetermined high-pitch position by pulling- .the counterweights outwardly until a scale 6| on the piston 5| that cooperates with a pointer 62 carried by the ring 51, indicates that the desired angular position has been reached. The lock nuts 58, which constitute the inner adjustable stops, may then be turned to engage the lugs 55 and there locked in position. By pushing the countcrweights 4| inwardly, the

blades may be turned to the low-pitch position, as

indicated by the scale BI, and the lock nuts 59 turned to engage the lugs 55. l

As shown in Figs. 1 and 2, the piston 5| is a cup-shaped memberthat operates on the outside of a cyhnder or sleeve 65 threaded into and constituting an extension of the cylindrical portion of the hub To prevent leakage of fluid from the piston I, the cylinder 65 isprovide'd at its forward end. with a packing ring 65. Fluid under pressure for operating the piston 5| is conducted from the hollow shaft 3 to the forward end of the cylinder 65 by means of .a tube or sleeve 61 secured by a coupling 68 in the end of the cylinder 65 and extending rearwardly into the end of the hollow shaft 3. At its inner end the sleeve 61 is provided with apa'cking ring 69 to prevent leakage at the position in which it engages the inner surface of the hollow shaft 3.

As shown in the structure illustrated in Fig. 1, the opening in the forward portion of the hollow shaft 3 is separated by a partition Ill from the opening in the remainder of the shaft, which carries the lubricating oil under pressure in a well known mamier. However, fluid pressure may be admitted to the forward portion of the shaft by way of openings 1| that extend radially from the hollow interior to the exterior of the shaft and communicate with an annular passageway in a sleeve 12 encircling the shaft 3 and supported in the forward end of the crank case 4.

Fluid pressure for the lubricating system and the propeller controlling system is generated by an engine driven pump 15, shown diagrammatically in Fig. 1, connected to be driven from the shaft 3. The pump may be of any-suitable type, such as an intermeshing gear pump, and it is supplied with oil through a supply conduit 16, leading from a container H, which represents the sump of the engine crank case I. From the pump l5 the oil is forced under pressure to the lubricating system. and through a pipe "I8 and suitable passageways 19 in the crank case 4, to the annular chamber in the sleeve 12, from which it flows through the passageways'll to the hollow shaft 8, and thence by the tube 61 to the piston 5|.

For effecting operation of the variable pitch propeller the fluid system may be provided with sump 11.

an adjustable spring pressed relief valve 8! similar to the standard relief valve ordinarily utilized in the pressure lubricating systemof an engine, In operating a fluid pressure control system of this type the pilot may adjustthe relief valve 82 to regulate the fluid pressure in the system and consequently to control the force exerted by the fluid upon the piston 5|.

If the pilot wishes to move the propeller to lowpitch position, it is merely necessary to increase the pressure exerted by the spring pressed valve by turning an operating handle 83, thereby building up sufli'cient pressure to move the piston 5| outwardly in opposition to the force exerted by the counterweights.

When it is desired to move the propeller blades from low-pitch to high-pitch position, the pilot may reduce the pressure in the fluid system by turning the operating handle 83 in the opposite direction and thus reduces the force exerted by the piston 5| to such extent that centrifugal force acting on the counterweights ll will overcome the fluid pressure force and move the blades to highpitch position.

To provide for controlling the pitch of the propeller without changing the pressure in the engine lubricating system, a three-way valve 85 may be connected in the passage-way 19 through the crank case 4 in such manner as to admit the full pressure of the fluid system to the shaft 3.

The valve maybe turned to cut oif the pressure from the oil pipe 18 and drain the oil from the piston 5|. As shown in section in Fig. 1, the

' three-way valve 85 comprises a rotatable sleeve when it is desired to move the propeller blades to low-pitch position the valve 85 is turned to the position shown for fluid pressure to actuate the piston 5|. to high-pitch position, the sleeve 85 may be turned to move the opening 81 out of alignment with the passageway 15, thus cutting off the pressure.

The oil may be drained from the piston 5|- by turning the valve 85 farther to bring the port 81 into communication with a pmgeway 88, through which the oil may flow from the piston 5| into a tube 88 that returns it to the engine The valve 85 may be operated from the pilots cockpit by cables or other suitable means in well known manner. Y

In operating an airplane equipped with my controllable pitch propeller, after the engine is started and while the airplane is on the ground, fluid pressure is admitted through the hollow shaft 3 to move the piston 5| outwardly, thus turning the blades 2 to low-pitch position, as defined by the adjustable stops 59. The propeller is thus adjusted to permit development of maximum power of the engine in the heavy load of the take-off. After the plane has attained the position of level flight, the fluid pressure on the piston 5| is released and the counterweights 8|, under the action of centrifugal force, turn the propeller blades to high-pitch position, bringing the lugs or the piston 5| into engagement with the stops 58.

The forces acting to twist the blades during flight, and the relations of these forces to each To change the propeller.

aosaam sitions are shown graphically in Fig. 11. In this figure the ordinates represent twisting moments about the bladeaxes in pound inches, and the abscissa represent the angular positions of the blades, which, of course, correspond to positions of the piston and of the counterweights. Corresponding positions of the piston,- counter 'weights, and the propeller blade are indicated in Fig. l and along the abscissa in Fig. 11 by the corresponding reference characters A, B and C, respectively.

The lower dotted curve in the diagram, indicated by the reference character E, represents the twisting moment'resulting from the inherent tendency of the blades to turn towards zero pitch position from the action of centrifugal force. The curve designated by the character F represents the twisting moment exerted upon the blades by the counterweights 4i and the connecting rods 52. It will be noted that this twisting moment is substantially double that inherent'within'the blades, and, as explained hereinbefore, acts in the opposite direction.

The counterweights 4 I'are preferably so shaped that the twisting moment F will, as nearly as possible, be uniform throughout the range of pitch-adjustment, as shown by the curve F of Figure 11.

i The solid line curve G represents the sum- ,mation of the curves E and F, that is to say,

' when the oil pressure is applied to the piston 51, the twisting moment exerted by it upon the blades is suflicient to overcome the twisting moment resulting 'from centrifugal force and to provide a comparatively large additional force for overcoming the frictional resistance'of the blades whichv results from the manner in which they are tightly fitted to the hub.

-I.rll-:ewise, it will be seen that when the oil pressure is released, the counterweights 4| in exerting the twisting moment F, overcome the twisting moment E exerted in the opposite direction by centrifugal force acting on the blades,

"constant, and consequently to. derive from the engine the maximum power of which it is capable at all times. To accomplish this, a system similar to that shown in Fig. 3 may be utilized, in which a gove'rnor mechanism90 is disposed in thefluid system between t he pump I5 and the v and propeller.

The pump L'i hollow engine shaft- 3 for goveming" the ad-" mission of pressure to the piston 5| in accord-' ance with the speed of rotation of the engine} maybe'the usual ,engine pump for supplying oil under pressure .to the engine lubricating system. From the pump a pipe' 9| leads to an annular chamber 92 surrounding the shaft 3, from which the oil passes through an opening .93 into the interior of the hollow shaft 3 at a position back of "the partition 10, for lubricating the engine in the usual manner. Another pipe94 extends from the pump 15 to the governor mechanism 90.

When the engine speed drops below a predetermined minimum, the governor is turned to ,the position shown in the drawings, in which position fluid pressure from the pipe 94 is permitted to pass through ports 95 into the interior of the governor, hence outwardly through ports 96 to a pipe 91 that leads to a sleeve 98 encircling the shaft 3 and having an annular chamber that communicates through an opening 99, to the interior of the hollow shaft 3 ahead of the partition 19.

. If the engine speed is increased above a predetermined limit, the valve body IOI in which the ports 95 and 96 are located, will be turned in response to the increased speedto move the ports out of alignment with the openings leading-to the pipes 94 and 97. As thevalve member IIli continues to-turn, ports 102 will be moved into communication with the pipe 91 to admit fluid from the propeller into the valve member IOI, and ports I03 will be moved to communicate with a drain pipe I04, through which the oil may drain back to the sump I7.

The mechanism of the governor 90 is shown in detail in Figs. 7, 8, 9 and 10'. The governor may be mounted in any convenient position in the airplane and is driven in synchronism with the engine by means of a flexible shaft, not shown, similar to the shaft ordinarily utilized on airplanes for driving the tachometer. The flexible shaft is connected in well known manner at the left end of the governor, as shown in Fig. '7, to the end of a shaft "I ID that rotates, consequently, at a speed directly proportional to the speed of rotation of the engine. The governor mechanism is supported by and enclosed within a suitable casing III in which the shaft III] is journalled.

Within the left end portion of the casing III are two governor weights H2, pivoted on a flange or wheel I I3, which is keyed to and revolves with the shaft I-IIl. As' best shown in the cross sectional view in Fig. 10, the weights II2 are each.

provided with an arcuate rack, or segmentmf an "internal gear H4 which engage, at diametrically opposite sides, a gear wheel II 5 that is rotatably mounted on the shaft I I0. Suitable coiled springs 6 are provided for holding the weights I I? at their innermost position when they are not being acted upon by centrifugal force.' The racks Ill and the gear I I5 are so arranged that when the weights I I 2 move from the inner position to their outer position, in the well known manner in which governors-of the fly-ball type operate, the gear wheel I I5 will be turned relative to the shaft III) through an angle of substantially 30.

'As shown in Fig. 7, the gear wheel H5 is secured to a sun' gear wheel I I! of similar size also rotatably supported on the shaft III! to turn with the gear wheel 5'. Meshing with the sun gear wheel II! are three planetary pinions H8, best shown in Fig. 9, that are'carriedon a spider. I I9 rotatably mounted on the shaft I i 0. The planetaiy gears I I 8 also mesh, at their outer edges, with an internal or ring gear I which surrounds the 'spider H9 and is secured to the inner surface of the. casing III in such manner that, during normal operation, the spider II9 will rotate within the'housingin, the direction of rotation of the 7 shaft H and at substantially one-half its speed.

Interposed between the planetary gears H8 in angular relation, and journaiied on the opposite face of the spider H9 is another set of planetary gears I2I. The planetary gears I2l mesh at their inner edges with a sun gear wheel I22 keyed to the shaft H0, and at their outer edges with a ring gear I23 carried by the valve member NH. The gear wheel I22 keyed to the shaft I Ill corresporids in general to the gear wheels I I and 'l I! journalled thereon, and the ring gear I23 on :the valve IUI corresponds in general to the ring gear secured in the casing III. If the shaft us is rotated slowly in suchmanner that governor weights 2 remain at their inner pesitions'the gear wheels llii, Ill and I22 all turn at the speed at which the shaft is rotated. Consequently, the spider I ill will progress in the saiiie direction at one-half speed, and, inasmuch as the sun gears, planetary gears and ring gears cm'resplond' to each other, the ring gear I23 on the valve IOI will remain stationary andthe planetary gears I2i will roll within it without changing the position of the valve JUL '5 If now we assume that the shaft III) is held stationary and the governor weights H2 are moved outwardly by some external force, the gear wheel 5 will be turned relative to the shaft H0 through substantially 30. Likewise, the sun gear wheel I" through 30, which will cause the spider Iii! to progress as a result of rotation of 'the planetary gears 'II8 within the ring gear I20. Inasmuch as the sun gear I22 is rigidly connected hr the shaft H0 and therefore held stationary, the planetary gears I2I will be caused to ratate by the progressing motion of the spider H9, and consequently the ring gear I23 will be caused to turn through an angle oi" 30 in the direction opposite to that in which the gear wheel "5 turns as the result of movement of the governor weights II2.

As the ring gear I23 moves through 30 angle, it causes the valve I 3| to move from the position shown in Fig. 3, in whiclr position the fluid pressure is admitted to the propeller mechanism, to the position in which the parts I 03 come into communication with the pipe 5:114 for draining oil from the propeller mechanism to the engine sump. y W i The same relative motions take piace when the shaft III! is rotating and ffthe governor weights "2 move under the action of centrifugal force.-

When the governor weights II2 rotate at a fixed radial position relative to the shaft 1 Ill, the ring gear I23 will remain: stationary in a position relative to the ring gear I20, depending upon the position of the wfeights relative to the shaft. However, upon moi fement of the weights in radial direction relative to the shaft IIII the ring gear I23 will be turned' relative to the ring gear I and the vgve body III! will be moved relative to the-casing III.

For the speed at which the governor will functinn to change the position of the valve I0 I, an operating lever I is provided at the right end bf the governor, to increase or decrease the pressure exerted by springs I3I, which oppijse rotation of the valve Illl. As best in 8, the springsISI are each connected fat one end by means of a pivot pin I32 to a disk or plate I33 secured to the valve body- Illl; At their other ends the springs I 3| are pivoted by pi1 s I34 at the ends of an arm I35 which is keyed to a stub shaft I35 that may be actuated by the operating lever I30. As may be seen Fig. 8, when of revolution at which the governor weights H2 will become effective to turn the valve "II is reduced, and the propeller will move from low pitch .to high pitch position at lower 'engine speed. Consequently, by means of the leverl 30, the speed of the engine may be regulated by changing the speed at which rotation ofjthe valve occurs.

Although I have described in detail certain specific embodiments of my invention it is'to be understood that the particular structures shown.

and the descriptions thereof are for the purpose only of disclosing complete and workable apparatus and it will be obvious to others skilled in the art that varius modifications in the details of construction of; the propeller and particularly in the auxiliary devices as valves and governing mechanism may be made without departing from the spirit and scope of the invention defined in the appended claims.

What If claim is:

1. A centrollable pitch propeller for aircraft, comprising a hub having radially extending arms, propeller blades rotatably journalled around the arms, fluid pressure operated means to move the blades to decrease their pitch at will, and to 1 overcome a contrary tendency of centrifugal force tending to increase the pitch of the blades, and counterweights mounted to revolve with the propeller and operative automatically? to increase the pitch of the blades by the action; of centrifugal force onflthe weights when the fluid pressure means is not operative. Z

2.-A controllable pitch propeller for aircraft, comprising a hub structure, blades rotatably .mountedron the hub, movable counterweights pivoted on the hub, linkage iconnectlng the counterweights to the blades effect change in the pitch of the blades in one direction by the action of centrifugal force on the counterweights, and manually controllable fluid-pressure operated means adapted to change the pitch in the other direction by overcoming the force of the counterweights. Q

3. In aircraft'tlriving apparatus, in combination, an engine shaft, a propeller driven by the engine shaft, constantly-operative means com-' prising 'centrifugally driven counter-weights tending to increase the pitch of the propeller in flight, an engine-operated fluid pump, a fluid system connected to the pump and operative at will Ito decrease the pitch of the propeller, and gov- Qerning means responsive to the engine speed for automatically controlling the fluid system, and ,fthereby the pitch of the propeller. I 4. In aircraft driving apparatus, in combination, an engine, a propeller driven by the engine,

means comprising movable counter-weights constantly operative during flight tending to increase the pitch of the propeller,;an engine-operated fluidpump, and a fluid system connected to the pump and operative at will to decrease the pitch of the propeller by overcoming the eifects of the counter-weights. a r

5. In aircraft driving apparatus, in combination, an engine, a propeiler driven by the engine,

meeting the counterweights to the blades to turn them under the action of centrifugal'force in one direction, a fluid-pressure actuated piston, and means connecting the piston to the counterweights to overcome the action of centrifugal force thereon for turning the blades in the other direction.

7. A controllable pitch propeller for engine driven airplanes, comprising a hub, propeller blades journalled' on the hub for pitch-adjusting rotation about their individual axes, adjustable stops to limit the movement of the blades in either direction to define a low-pitch and a highpitch position. centrifugally-actuated means comprising counter-weights carried by the. hub

for moving the blades during flight to the high a pitch position, and controllable means driven by the engine for overcoming the action of the centrifugally'actuated means to move the blades to the low-pitch position.

8. In a controllable pitch propeller for ,-aircraft, comprising a hub structure, blades rotatably mounted on the hub, movable counterweights pivoted on the hub, and linkage connecting'the counterweights to the blades at a point intermediate the free and'pivoted ends of the counterweights toelfect change in the pitch of the blades in one direction by the action of centrifugal force on the counterweights, said counterweights and linkage being so shaped and connected that the torque exerted to turn the blades is substantially constant throughout the weights at will.

range of movement of'the counterweight, and means to overcome the effect of the counter- 9. In a controllablepitch propeller for aircraft, comprising a hub, blades mounted on the hub and rotatable on their longitudinal axes for pitch adjustment, levers pivotally. attached to the hub at one end, the free'ends of the levers conhub, propeller blades journalled on the hub for,

stituting counterweights, intermediate parts of the levers being connected to linkage attached to the blades, the lever being curvedand proportioned and the linkage being arranged so that as centrifugal force acting on the weight increases with outward movement of the weight, the leverage effective to turn the blades varies inversely as the increase of centrifugal force due to position of the weight, such construction being adapted to apply substantially uniform turning moment to increase the pitch ofthe blade -at.al1 positions of the counterweights, and means to overcome the effect of the counterweights to restore the blades to low-pitch position at will.

10. A controllable pitch propeller comprising a pitch-adjusting rotation about their individual axes, adjustable stops to positively limit the movement of theblades in either direction to'define a low-pitch and a high-pitch position. positive stops to limit the maximum movement of the.

blades in .eitherdirectioii, and means for moving the blades duringflight.-

11. A controllable pitch propeller comprising a hub portion having tapered integral extensions with a lubricant retaining pocket in the surface thereof, blades journalled on the extensions. counter-weights carried by the hub, means connecting the counter-weights to the blades to turn them under the action of centrifugal force in one direction, a fluid pressure actuated piston, and means connecting the piston to the counterweights to overcome the action of centrifugal force thereon for turning the blades in the other direction, the blades having a hardened steel interior bearing constituting the portion that is journalled on the hub extensions.

'12. A variable pitch propeller comprising a plurality of blades, means for rotating said blades, means responsive to centrifugal force for increasing the pitch of the blades, and fluid pressure operated means opposing the operation of said centrifugally responsive means for decreasing the pitch of the blades.

13. A variable pitch propeller comprising a plurality of blades, means for rotating said blades, means responsive to centrifugal force for increasing the pitch or the blades, and fluid pressure operated means for controlling-the operation of said centrifugally-responsive means.

14. A variable pitch propeller comprising a plurality of blades, means for rotating said blades, means responsive to centrifugal force for increasing the pitch'of the blades, and other means for decreasing the pitch of said blades including plurality of blades, means for rotating said blades.

means responsive to centrifugal force for increasing the pitch of the blades, fluid pressure operated means for decreasing the pitch of the blades, and means for controlling the operation 01 pressure operated means.

16. A variable pitch propeller comprising aplurality-of blades, means for rotating said blades,

means responsive to centrifugal force for increas-' ing the pitch of the blades, fluid pressure operated means for decreasing the pitch oi'the blades, and a governor responsive to changes in the 'rate I of rotation of said blades for controlling the operation of said fluid pressure operated means. 17. A variable pitch propeller comprising a.

' plurality of blades, means for rotating said blades,

means responsive to centrifugal force for increasing the pitch of the blades, fluid pressure operated means for controlling'operation of said centrifugally responsivemeans, and means for controlling the operation of said fluid pressure operated means. v

18. A variable pitch propeller comprising aplurality of blades, means'for rotating said blades, means responsive to centrifugal force for increasing the pitch ofthe blades, fluid pressure operated means for controlling the operation of said centrifugally responsive means, and a governor r'esponsive to changes in the rate of rotation of said pressure operated means.

v19. A variable pitch propeller comprising a plurality of blades, means for rotating said blades, means responsive to centrifugal force for varying the pitch ofsaid blades, means operable in accordance with the increase in volume of a fluid the fluid .blades for 'controlling'the operation of said fluid.

container for controlling the operation of said centrifugally responsive means, and means for the pitch of said blades, means operable in accordance with the increase in volume of a fluid container for controlling the operation of said centrifugally responsive means, and means for controlling the increase in volume of said 'fluid container, said last named means including a governor responsive to changes in the rate of rotation of said blades.

21. In combination with a rotatable shaft, a

propeller hub drivably connected thereto, a plurality of propeller blades rotatably mounted on said hub, means for rotating said blades on said hub to vary the pitch thereof, said means including a fluid operated expansible chamber device, and means including a plurality of manually adjustable and independently acting devices for selectively predetermining the extent of operation of said fluid operated expansible chamber.

' 22. A controllable pitch propeller comprising a plurality of blades, means for rotating said blades, means responsive to centrifugal force to effect changes in the pitch of the blades in one direction by the action of centrifugal force-on said means, and manually controllable fluid pressure operated means adapted to change the pitch of the blades in the other direction by overcoinpitch of the blades in one direction by the action of centrifugal force on the counterweights and manually controllable fluid pressure operated means adapted to change the pitch in the'other I direction by overcoming the force of the counterweights.

24. A controllable pitch propeller for aircraft, comprising a hub structure, blades rotatably mounted relative to the hub, counterweights connected to theblades to effect change in the pitch of the blades in one direction by the action of centrifugal force on the counterweights, and controllable fluid pressure operated means adapted to change the pitch in the other direction by overcoming the force of the counterweights and governing means responsive to the speed of rotation of said propeller for automatically controlling the fluid pressure operated means.

25. A controllable pitch propeller comprising a hub portion, blades journalled on the hub,-

counterweights connected to the blades to turn them under the action of centrifugal force in one direction, a fluid pressure actuated piston and means connecting the piston to the counterweights to overcome the action of centrifugal force thereon for turning the blades in the other direction.

26. In aircraft driving means, the combination of an engine shaft, a propeller driven thereby, an

engine-operated fluid pump, a fluid conducting system, including fluid pressure means, connected hub, counterweights connected, to the blades to turn them in onedirection under the influence of centrifugal force, fluid pressure actuated piston and means connecting the piston to the blades to overcome the action of centrifugal force and turn the blades in the other direction.

FRANK W. CALD WELL. 

